CafeNet El Sol offers a reservation service for a fee of US$30, or $10 for one-day passes; details on their Corcovado page. The previous text is in English. Here is a translation to Swahili:
CafeNet El Sol hutoa huduma ya kuhifadhi kwa ada ya dola 30 za Kimarekani na pasi za siku moja kwa dola 10 za kimarekani; maelezo kwenye ukurasa wao wa Corcovado.